Solved! (was Re: [GRASS-user] v.dissolve - is this a bug?)

Richard Chirgwin rchirgwin at
Thu Sep 16 00:51:11 EDT 2010

  In case anyone's wondering, I found out what happens.

The issue is the handling of case by the OSX command line. Most of the 
time, the OSX command line ignores case. For example:

v.clean MyMap output=CleanMap option=break,snap
works the same as:
v.clean mymap output=cleanmap option=break,snap

The only difference is that the output file name is cased - but a 
case-less input of a cased name works.

However, database handling is sometimes case-sensitive. If I create the 
column using v.db.addcol:

v.db.addcol MyMap columns="Dissolve int"

then these will behave the same:
v.db.update MyMap column=dissolve value=1
v.db.update MyMap column=Dissolve value=1

However, v.dissolve will notice the difference!
v.dissolve MyMap output=MyMap_Dissolved column=Dissolve -- works
v.dissolve MyMap output=MyMap_Dissolved column=dissolve
ERROR: Key column must be of type integer or string

I would file this in the tracker, but there's nobody around to reset my 

So: in using v.dissolve, beware of case.


On 16/08/10 6:08 PM, Markus Neteler wrote:
> On Sat, Aug 14, 2010 at 10:16 AM, Richard Chirgwin
> <rchirgwin at>  wrote:
>> Hi,
>> In running v.dissolve within a script, I am getting an intermittent failure:
>> ERROR: key column must be integer or string
>> Here's the script spot that fails (but only sometimes)
>> v.db.addtable MAP
>> v.db.addcol MAP columns="Dissolve int"
> At this point, please run
> -c MAP
> and report here.
>> v.db.update MAP column=Dissolve value=1
>> v.dissolve MAP output=DISSOLVE column=Dissolve
>> The killer is that it isn't reliable - sometimes it works, sometimes it
>> fails, and I can't tell why!
> Always on the same machine, the same binary and the same map?
> Markus

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